The following slides describe the processing and duplicating of x-ray films and quality control in dental radiography.

Processing DuplicatingQuality Control

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Film ProcessingAfter the films are exposed to radiation, they need to be processed in order to see the information on the film. This processing is done using special chemicals and takes place in a darkroom. The darkroom should have the following attributes:

• It must be light-tight. Since the silver halide crystals are sensitive to both x-rays and light, the area where films are processed must be completely dark, except for a safelight (see next slide).• It must have hot and cold water available; a mixing valve, which regulates temperature, is recommended.• It should have an adequate size and must be kept very clean (no spilled chemicals).

Safelight

Safelights are used in the darkroom to provide adequate light so that you can see what you are doing when you unwrap films for processing. The safelights have special filters that produce light that does not expose the film.

D-speed Intraoral,

extraoral

Safelight Filters

Morlite GBX-2

There are two filters currently available: an orange one (Morlite) and a red one (GBX-2). The orange one can only be used for D-speed film. The red one can be used for all film types (D-speed, F-speed, extraoral, and duplicating). Since most offices use both intraoral and extraoral film, it makes sense to always have a red filter. The new Kodak LED red filter (below right) provides more light than the older safelights.

Safelighting (continued)

The safelight should have a 15-watt bulb (older style safelight) and be mounted to the wall or ceiling at least 4 feet from the area where the films are unwrapped and loaded into the film processor.

15 watt bulb

4 feet

red filter

15 W

film fogging

If you have a light leak or improper safelighting in the darkroom, the film may be fogged before it is processed. Film fogging is the exposure of more of the silver halide crystals than would normally be affected during the taking of a radiograph. The exposure of these extra crystals results in the film being darker than normal and will usually decrease the diagnostic value of the film. If a film is processed without being exposed to light or x-rays, it should come out completely clear (white on the viewbox). A fogged film will have an overall slight grayness (see below).

clear, unfogged film

Film Fogging

Light Test

In order to check for improper safelighting or light leaks, you can perform the following test. Unwrap a film in the darkroom and lay it on the top of the processor. Place metallic (opaque) objects on the film (coins below left) and wait for 3-4 minutes. Remove the objects and process the film. If the film comes out completely clear, everything is OK (below right). If you see the clear images of the metallic objects surrounded by gray, there is a light problem (below middle). Correct as needed.

Latent Image

When you take a radiograph, x-rays penetrate through the tissues and interact with the silver halide crystals on the film, creating exposure centers in the crystals. There are thousands of these crystals and the number that are affected is dependent on the number of x-rays reaching a particular area of the film. Many x-rays will penetrate through objects that have little density, such as air and soft tissue. Few, if any, x-rays will penetrate objects with high density, such as amalgam and gold restorations. This difference in x-ray penetration results in the formation of a pattern on the film known as the latent image. Latent means “hidden”; the image formed by the pattern can not be seen until the film is processed (see next slide).

Latent Image

Many x-rays penetrate and expose many silver halide crystals

Fewer x-rays penetrate and not as many silver halide crystals are exposed

Few, if any, x-rays penetrate; silver halide crystals not exposed

Air/soft tissue Bone Amalgam/gold

= Exposure centers

Basic Steps of Processing

1. Development: exposed silver halide crystals converted to black metallic silver.

2. Rinsing: Used with manual processing only; developer solution removed from film before fixing

3. Fixing: unexposed silver halide crystals removed from film

4. Washing: all chemicals removed from film

5. Drying: after removing moisture, films can be handled for mounting

After taking the films on the patient, they are taken to the darkroom for processing. The steps involved in processing are:

Air/soft tissue Bone Amalgam/gold

Developing

Development centers in crystals struck by x-rays are converted into black metallic silver

Air/soft tissue Bone Amalgam/gold

Developing (continued)

Entire crystal converted to black metallic silver

Developing (continued)

The crystals that do not have exposure centers are not affected by the developer if films are in the developer for the correct amount of time and the temperature of the developer is correct. However, if the films are left in the developer too long, or the temperature is too high, the developer will start to act on the crystals that were not exposed by x-rays (no exposure centers) and these crystals will also be converted to black metallic silver. This results in the film being darker than ideal.

After the films are properly developed, they go into the fixing solution. (The films are rinsed first if using manual processing).

Air/soft tissue Bone Amalgam/gold

Fixing

In the fixing solution, the unexposed silver halide crystals are removed from the film by the fixing solution.

After the films have been in the fixing solution for the specified time, the films are washed and then dried so that they can be mounted for viewing.

The next two slides review the components of the developing and fixing solutions.

Developing Solution

Developer: Coverts exposed silver halide crystals into black metallic silver

Preservative: Helps protect the developer from being oxidized by the air

Activator: Provides alkaline solution needed by developer; also softens gelatin, allowing developer to reach crystals

Restrainer: Reduces effects of developer on unexposed crystals

Fixing Solution

Clearing Agent: dissolves and removes unexposed silver halide crystals from emulsion

Preservative: Inhibits decomposition (oxidation) of clearing agent

Acidifier: Neutralizes any contaminating alkali from the developer

Hardener: Hardens emulsion so film can be handled

Automatic vs. Manual Processing

Most offices use an automatic processor for film development. While it will produce a very good film if done properly, manual processing is very time and labor intensive, requiring a much longer processing time than automatic processing and requiring someone to be available to transfer films into the various solutions. Drying films also takes much longer.

The following slides discuss both types of processing.

Manual Processing

Cold

Hot

Mixing valve

Fixer insert tank

Developer insert tank

overflow tubedrain

waterbath (large tank)

water inlet

With manual processing, two tanks, one containing developer and one fixer, are placed in a larger tank filled with water. The water is maintained at a certain temperature using a mixing valve. The film is first placed in the developer for a specified time, rinsed in the water, and then placed in the fixer. After fixing for the appropriate time, the film is washed in the water. The overflow tube prevents water from rising high enough to enter the developer or fixer tanks.

Manual Processing

For manual processing, films are clipped to some type of film hanger (see below). The film should be handled only by the edges to avoid damage. The film hanger, with films attached, is then placed in the processing solutions, developer first. If the film is inadvertently placed in the fixer first, the film will come out completely clear (no image); the fixer removes all crystals that have not been converted to black metallic silver by the developer, even if they have exposure centers.

Develop 5 minutes at 68 degrees

Rinse 30 seconds (agitate continuously)

Fix 4 minutes (Agitate intermittently; 5 seconds every 30 seconds)

Wash 10 minutes in clean running water

Hang films to dry

Manual Processing Times

Manual Processing

lid

Place hanger with films attached into the developer for 5 minutes. The lid is placed over the tank if you plan to leave the darkroom during development. (Click to complete this action).

The silver halide crystals on the film are converted to black metallic silver in the developer. (Click to see the films change from pink to dark gray).

After removing the lid, place the films in the rinse water and continuously agitate for 30 seconds. Next put the films in the fixer for 4 minutes and agitate for 5 seconds every 30 seconds. (Click to complete these actions)

Remove the films from the fixer and place in the water bath for 10 minutes. (Click to place films in water).

Remove film from the wash water and hang films to dry. (Click to complete action).

Manual Processing

When processing films manually, it is important to check the solution levels at least once each day. If the solution level is too low, the films at the top of the film hanger may not be covered and will not be developed and/or fixed properly.The solution should be stirred frequently; the chemicals tend to settle to the bottom and need to be recirculated for optimum performance.You should check the solution temperatures often. The amount of time needed to develop the films is dependent on the temperature of the solutions. If the temperature is too low, more development time is needed. Too high a temperature requires less time in the developer. See next slide for the ideal time and temperature.

ReplenishmentSolutions tend to become depleted as more films are processed. This leads to inadequate developing and/or fixing and film quality will be decreased. To prevent this, it is important to replenish the solutions by adding 8 ounces of chemical (both developer and fixer) each day. This will maintain the quality of the solutions for up to 30 films processed during the day. If more than 30 films are processed, additional solution must be added at a rate of 1 ounce for every 4 films over 30.

Film Exit

Dryer (heater, fan)

FilmEntry

Wash

Automatic ProcessorAutomatic processors come in various shapes and sizes, but they all function the same. The film is inserted in the inlet slot where it is fed into a series of rollers (see photo next slide). These rollers transport the film through the developer, fixer, wash and dryer and the film exits the processor ready to mount. The rollers “squeegie” the excess chemicals off of the film as it exits each solution; no rinse is needed between the developer and fixer. (Click to process film).

FixerDeveloper

Automatic Processor

insert film

sdeveloper

fixer

dryer

wash

The photo below shows the insides of an automatic processor. The wash section is located below the drying rack. (See diagram on previous slide).

Automatic Processing

The manufacturer’s of automatic processors identify the ideal temperature to be used in processing. You should follow their recommendations.

As with manual processing, the solutions should be replenished daily. Add 8 ounces of developer and fixer for up to 30 films. Add one ounce of chemical for every four films over 30.

The above information pertains to intraoral films. If panoramic films are processed, they will deplete the chemicals more quickly, because of their size, and more frequent replenishment is needed.

Automatic Processing

Roller Transport Clean-up Film should be used each day to clean the rollers before beginning film processing.

The processors should be cleaned at every solution change, which should be done every 2-4 weeks depending on the number of films taken.Rollers should be cleaned with warm water using a soft brush. Follow manufacturer’s instructions for cleaning the processor. (Refer to the owner’s manual).

Daylight Loader

Daylight LoaderA daylight loader may be used if there is not enough room in the dental office for a darkroom. It can be used for intraoral films only (pans too large) and should be located in an area with reduced lighting. The unopened film packets are placed in the loader through the lid in the top and, after closing the lid, the operator reaches through the rubber cuffs, opens the films and puts them in the processor.

lid

rubber cuffs

Processing Errors

The following slides identify some of the errors commonly seen in film processing.

too dark correct density too light

The density of the film can be affected by problems in the darkroom, resulting in a film that is too light (below right) or too dark (below left). These changes in film density are discussed in the following five slides.

Film Density

• Developer too hot

• Too much time in the developer

• Exposure to light (opening door, turning on light, light leaks around door, incorrect or

cracked filters)

Dark Film

A dark film can result from any of the following:

90°F 95°F68°F 80°F

Developer too hot

5 minutes development time for all films

If the films are kept in the developer for the correct amount of time but the developer is too hot, the film will get darker as the temperature increases (see below).

All films processed at 68° F

15 min. 20 min.5 min. 10 min.

Too much time in the developer

If the films are kept in the developer too long, even though the temperature is correct, the film will get darker as the time increases (see below). Notice that the effects are less pronounced with changes in time than they are with a change in temperature as seen on previous slide.

The completely black area on the right side of the film below is caused by light exposing the film when the darkroom light (not safelight) was inadvertently turned on before the film was completely in the automatic processor. (The tightness of the rollers against the film prevented light from reaching the front part of the film). Opening the door during processing could also create this problem. Light leaks or faulty safelighting would result in an overall darkening of the film, similar to too high a temperature.

Exposure to light

Light Film

• Developer too cold

• Not enough time in the developer

• Under replenishment (developer gets weak)

• Contaminated developer

• Excessive fixation

A light film can result from any of the following:

Dark spots – developer contamination

If drops of developer accidentally contact the film prior to processing, the developing action will start to act on these areas immediately. When the film is then placed in the developer, the overall time that these areas are developed is longer than for the rest of the film, resulting in darker spots.

Light spots – fixer contamination

If drops of fixer accidentally contact the film prior to processing, the fixing action will start to act on these areas immediately. When the film is then placed in the developer, there are fewer crystals to be converted to black metallic silver, resulting in lighter spots. Usually the contamination is on one side of the film only so that the crystals in the emulsion on the opposite side are processed normally and you can still see part of the image.

Yellow/brown stain – depleted fixer

If the film is not adequately fixed, the undeveloped crystals (those without exposure centers) will not be removed from the film, resulting in a yellowish-brown stain. This is more apparent in the film below in the areas that were not exposed to x-rays. The left side of the film represents a cone cut (dotted lines) and the areas in the crowns represent amalgam or gold restorations.

Films overlapped during processing

If films are fed into the automatic processor too quickly, the films may overlap each other, preventing the processing chemicals from acting on the overlapped emulsions. This results in a dark area on each film (see below).

Dark lines

If the automatic processor is not cleaned properly, the rollers may become dirty . This results in black lines on the film (see below).

Static electricity

If the film is removed too quickly from the packet (intraoral) or from the film box or cassette (extraoral), contact with overlying materials may create friction, resulting in a static discharge. This may create black dots, lines, “lightning bolts”, or tree-branch patterns (see below).

Duplicating

It is often necessary to send a copy of films to another general dentist, a specialist, or to obtain a preauthorization from the insurance company. In order to get this copy, the film needs to be duplicated.

A duplicate film is made by directing a light source through the original film onto special duplicating film. This is most effectively done using a commercial duplicator (see below). A red safelight is used (GBX-2, LED).

Duplicating (continued)

The original film must be in tight contact with the duplicating film. This is accomplished by closing the lid on the duplicator and locking it or pushing down on it.

Duplicating film has a single emulsion layer. The emulsion side must be in contact with the original film.

Duplicating film is a direct positive film, meaning that it gives a positive, or duplicate, image of the original film. If you increase the amount of time the light is on, the duplicate film will be lighter; less light exposure creates a darker duplicate film.

Original Duplicate

If done properly, a duplicate film will provide most of the diagnostic information needed (see below). However, duplicate films are never as good as the original.

Original Duplicate

If not done properly, duplicate films will be of little value in trying to make a diagnosis. Films should always be removed from film mounts before duplicating in order to insure tight contact between the original and duplicate films. Lack of tight contact produced the duplicate film below.

Quality Assurance

The definition of quality assurance listed in NCRP Report No. 145 (December, 2003) is:

“The mechanisms to ensure continuously optimal functioning of both technical and operational aspects of radiologic procedures to produce maximal diagnostic information while minimizing patient radiation exposure.”

Quality Assurance: ComponentsThe technical and operational aspects of radiologic procedures include:

1. X-ray units: These need to be inspected by a qualified expert at regular intervals to ensure proper performance

2. X-ray Film: The film needs to be used before the expiration date and stored appropraitely

3. Technique: The operator must use proper technique in taking films

4. Processing: Optimal performance needs to be evaluated daily using quality control tests

5. Viewing conditions: Proper viewing conditions need to be maintained for optimal diagnoses

Quality Assurance: Benefits

The benefits of a good quality assurance program are:

1. Improved diagnosis: if the quality of the films is optimized, the films will provide the best diagnostic information

2. Reduced patient exposure: if the x-ray machine is working properly and no retakes are needed (due to faulty technique or processing), patient exposure will be minimized

3. Time and cost savings: If everything is done properly, and no retakes are necessary, the operator won’t need to devote excess time to retaking films and fewer films will be used.

Quality Assurance: Methods

The methods that can be used to provide quality assurance include:

1. Scheduling an equipment inspection through the State Radiologic Health Department

2. Reviewing the technical capabilities of the personnel taking the radiographs and providing training as needed, including continuing education required by the state

3. Daily monitoring of equipment and viewing conditons

4. Quality Control tests (see next slide)

Quality Control Tests

Quality Control Tests are primarily used to identify problems with the processing of films but may also identify problems with the x-ray equipment. Quality Control Tests include:

Reference Radiograph: A properly exposed and processed film is kept on the viewbox. Each day a new film is exposed and processed and compared to the reference radiograph. Differences in the films may indicate a problem. This is the least reliable test.

Quality Control Tests (continued)Step Wedge: an aluminum step wedge (see below) with varying thicknesses of aluminum (steps) is placed on a film packet and exposed with standard exposure settings. It is then processed under ideal conditions (processor cleaned with new solutions). Each day a new film is exposed and processed using the step wedge. These daily films are compared to the original (ideal) film. (see next slide).

Step Wedge pattern on film

lead bar

aluminum steps

White (clear)area on filmrepresentslead bar

If the steps on the daily film line up with the steps on the original film (same densities) the test is considered negative. This indicates that everything is satisfactory and no changes are needed.

Original film

Daily film

Same densities oncorresponding steps

Original film

Daily film

If the steps on the daily film do not line up with the steps on the original film (different densities) the test is considered positive. This indicates that there is a problem that needs to be corrected. The most likely problem is with processing. If you clean the processor and add new solutions and the steps on a new film still do not line up, the problem is probably with the x-ray equipment.

Different densities oncorresponding steps

This concludes the section on Processing, Duplicating and Quality Control. Additional self-study modules are available at: http://dent.osu.edu/radiology/resources.htm

If you have any questions, you may e-mail me at: jaynes.1@osu.edu

Robert M. Jaynes, DDS, MSDirector, Radiology GroupCollege of DentistryOhio State University